The first sex scene in “Blue Is the Warmest Color,” Abdellatif Kechiche’s French coming-of-age drama about a young lesbian couple, lasts longer than any other sequence in the movie. To dwell on its length, however, shortchanges its relevance to this three-hour-long feature. After a brief heterosexual relationship in which she loses her virginity, 15-year-old Adéle (Adéle Exarchopoulos) falls hard for chic art student Emma (Léa Seydoux), and the moment they get the chance to take their clothes off the passion explodes. In the cavalcade of kissing, licking, slapping and moaning that follows, Kechiche makes apparent the intensity of their physical bond, which later enhances the heartbreak caused by watching it fall apart.

Exarchopoulos delivers a bold, thoroughly credible breakthrough performance at the movie’s center, portraying her character as a woman trapped by the mixed messages around her. At school, her peers encourage her to date a male classmate who has his eye on her, but balk when they figure out she’s dating a woman. Seydoux, barely recognizable during the first half under a mop of blue-dyed hair, perfectly embodies the freewheeling mentality that offers Adéle an escape from her staid existence. Their commitments to these characters carry the narrative.

But Kechiche’s screenplay, which draws Julie Maroh’s graphic novel, manages to convey the depth of feeling shared by the couple so well partly by taking his time. “Blue is the Warmest Color” is divided into two parts that take place over the course of several years (the official French title is “The Life of Adele Chapters 1 and 2”). In the first, the soft-spoken Adele meets Emma in a gay bar and gradually develops a bond with her, fascinated by the slightly older woman’s sly gaze and philosophical insights. Years later, as Adéle starts her professional life and her interests mature, the relationship starts to strain for the usual reasons. It’s not exactly surprise when things go awry, but by the time the arguments begin, Kechiche has crafted such a believable world that it’s hard not to get wrapped up in the stakes at hand.

In that regard, sex is less the main ingredient in “Blue is the Warmest Color” than the overall ways that physicality impacts romantic attraction. While America reacts to fleeting glimpses of breasts and awkward thrusting on “Girls,” Kechiche depicts the sensuality of his dual heroines with the same compassion visible in other scenes. A crucial moment when tensions come to the fore with one woman in tears and the other screeching in anger, provides an extraordinary counterpoint to the eroticism shown earlier.

Much of the movie is concerned with the slow, hesitant means by which Adéle comes out of her shell, particularly whether she needs Emma’s help to do it or must take on the task solo. Their faces are crucial to deepening the plot. In one remarkable scene shortly after they start sleeping together, Emma and Adéle attend a gay pride parade, sticking close together while registering vastly different responses to their surroundings: As Emma giddily dances around, Adéle appears intensely shy. Yet in the second chapter, she’s seen rocking the dance floor with an alluring swagger. Kechiche excels at capturing his protagonist’s emergence in the world.

The unconventional length for a story of this nature makes some parts more bearable than others. Most supporting characters, including other potential love interests, parents and co-workers, suffer from a lack of the same development allotted to the two leads. But in that same regard Kechiche creates a fleshed out environment too big for one movie to contain. Its structure certainly makes the possibility of a sequel worthy of consideration.

Kechiche most successful feature to date, “The Secret of the Grain,” dealt with the vastly different terrain of immigration and class issues. With his latest project, the director’s approach echoes the textured personal elements of Olivier Assayas in his smaller projects, where implication carries more depth than dialogue. Though nobody states it outright, “Blue is the Warmest Color” elegantly tussles with the idea of reconciling desire with other factors involved in the cultivation of healthy companionship. In Adéle’s case, the story continues.

Criticwire grade: A-

HOW WILL IT PLAY? A well-received Cannes competition entry recently picked up by Sundance Selects, the film should perform decently in limited theatrical release due to strong reviews but will mainly succeed on VOD due to the sex factor.